Umbercode on "conditionals (e.g. is_page()) do not work in head?"

I noticed that checking for type of page with is_singular() etc. does not (or no longer?) work in the head of the page? Neither doing it directly nor using the wp_head action.
Oddly enough, Wordpress uses this construct itself for several things amongst which is the inclusion of meta-canonical which now shows up on every page not just singular ones (look at line 2405 in link-template.php).
Is this a bug, intended or am I doing something wrong?